Ideally, when leaders talk about "employee engagement," they're referring to discretionary effort. They want workers who are so invested in the company's mission that they go above and beyond the call of duty. This winds up a win-win: Managers get the team's best effort, and employees love their jobs.

"The problem with 'employee engagement' as a term is that it has too often been used as a stand in description for 'employee satisfaction,'" writes Bernice Bowmaker-Falconer at HR Focus. "Engagement is not satisfaction. Yes, it is true that a happier or more satisfied employee is more likely to have an increased level of discretionary effort, but more importantly--there are employees [who] are happy simply because they don't feel the need to do much."

What if the offer you're getting from these consulting groups isn't an increase in discretionary effort, but increased alignment between your employees' professional and personal goals? That doesn't sound so bad in theory. Here at Build, we're strong advocates of the importance of work-life balance. But it's easy to see where this mind-set can go wrong if work isn't very high on your employees' priority list.

In fact, a recent study by the consultancy group Leadership IQ tied performance reviews to engagement levels. At a full 42 percent of firms studied, low-performance workers rated as the most engaged. "Low performers often end up with the easiest jobs because managers don't ask much of them," Mark Murphy (@LeadershipIQ), CEO at the consultancy, tells the Wall Street Journal.

That scenario almost certainly isn't what you have in mind when you think about improving your team's engagement levels. So the next time you're approached by someone who wants you to pay them for help, make sure you ask them exactly what they mean by "engagement."